Many of the micro-switches now used in electrical and electromechanical applications are mechanical type switches. Mechanical switches, however, are prone to several problems. For example, current flow through the contacts can lead to electrical erosion, and the continued opening and closing of the contacts can lead to wear or damage. Furthermore, contact bounce frequently occurs whenever contact switches are used.
To reduce these problems, optical switches have been developed which require minimal mechanical action. In optical switches, instead of one contact mechanically meeting another contact, a light source impinges on a light-sensing device to provide current flow through the switch.
An example of an optical switch is disclosed in U.S. Pat. No. 3,949,219 issued to Crouse. An optical path interconnecting two cavities is opened or blocked by the movement of a opaque plunger having a plurality of apertures. The switch may be converted from a normally open to a normally closed switch, or vice versa, by rotation of the plunger to alternately select the aperture in the plunger which may be placed in register with the optical path. Rotation of the plunger to convert the switch requires several steps. First, the plunger must be pushed into the top portion of the housing until a shaft portion passes through a bottom opening. Then, the plunger must be rotated by 90.degree.. Then, the plunger must be reinserted into the housing into its original position. This switch requires the use of two input leads and two output leads.
It is an object of the present invention to provide an optical switch which can be easily converted from a normally open to a normally closed switch, or vice versa. Another object of this invention is to provide a three terminal optical switch. Still another object is to provide an effective method of mass-producing such optical switches.